Gauge casing having plastic hinged blow-out



Aug. 24, 1965 H. w. HOFF, JR

GAUGE CASING HAVING PLASTIC HINGED BLOW-OUT 2 Sheets-Sheet 1 Filed Nov. 50, 1961 INVENTOR fl mer W1 flu/F, J4.

ATTO R Aug. 24, 1965 H. w. HOFF, JR 3,201,992

GAUGE CASING HAVING PLASTIC HINGED BLOW-OUT Filed Nov. 50, 1961 2 Sheets-Sheet 2 INVENTOR flax/er M Hof J4.

ATTORNE S United States Patent v 3,201,992 GAUGE CASING HAVING PLASTIC HINGED BLOW-OUT Harry W. Hofi, .lr., Quakertown, Pa, assignor to Ametek, Inc., a corporation of Delaware Filed Nov. 30, 1961, Ser. No. 155,972 11 Claims. (Cl. 73-416) The present invention relates to pressure gages and particularly to a new and improved back construction for relieving pressure that may develop within the gage case upon the failure of the pressure responsive element therein.

7 It is known to provide hinged back plates for pressure gages. These back plates ordinarily are provided with spring means for maintaining them in closed condition. Consequently, when it is desired to make adjustments to the internal mechanism that is only accessible from the back, it is necessary to hold the spring-closed back cover open with one hand while making the adjustment with the other hand. This presents an awkward arrangement since generally any adjustment usually requires both hands.

The principal object of this invention is to provide a back face cover for a pressure gage that will automatically open upon the buildup of pressure within the gage casing and remain open until manually closed.

. Another object of the invention is to provide such a back face for a pressure gage that has an integral part thereof in the form of a hinged construction.

Still another object of the invention is to provide such a gage back cover that includes as an integral part thereof an edge construction that will cooperate with an intermeshing construction on the gage casing.

' Still another object of the invention is to provide such agage back cover that includes a pressure sensitive area which, when subjected to pressure within the casing, will separate the intermeshing connection between the back face cover and the casing.

' Still another object of the invention is to provide such a gage and back cover plate with mounting means for mounting the gage on a back board sufliciently far from the back board so that the back cover plate can open to relieve pressure within the casing and such that the back board will intercept any parts that might be blown from the interior of the case upon the failure of the pressure responsive element of the gage.

In one aspect of the invention, the gage casing may be providedwith a substantially cylindrical back end portion on which may be located mounting bosses for cooperation with spacers fixed to a mounting board.

In another aspect of the invention, the casing may be provided with a circular opening in its back leading to the interiorof the casing, having a thin lip formed on the innerperipheral edge of the circular opening and a groove of greater diameter in said inner peripheral edge inwardly of said lip construction.

In another aspect of the invention, the back cover plate may be substantially circular in form and made from a plastic material in which its crystalline nature permits substantial increases in strength through orientation or stretching, has high elongation beyond the yield point, has resistance to stress cracking, and forms a relatively tough skin during molding or extruding. Although flexible plastics such as vinyls and polyethylenes possess to some degree the above desirable characteristics, a plastic material of exceptional qualities is one such as polypropylene.

In another aspect of the invention, a substantially cir- Cularfl plastic back cover plate' made from such material may include a groove reducing the cross sectional thickness of the plastic material along a segmental line. Flex- 3,201,992 Patented Aug. 24, 1965 ing the segmental parts of the plate on each side of the groove forms a hinge of the plastic material itself.

In still another aspect of the invention, the peripheral edge of the back plate on one side of the hinge groove may be provided with two spaced peripheral lips forming a peripheral groove therebetween that receives the lip on the inner peripheral circular edge of the back opening of the casing when the back plate is closed.

In still another aspect of the invention, the peripheral edge of the back plate on the opposite side of the hinge groove may include a flange for fitting Within the groove interiorly of the lip on the casing opening.

A still further aspect of the invention may include an area portion of the back plate segment that opens, which will act as a diaphragm tending to unlatch the openable portion of the back plate upon the buildup of pressure within the casing.

The above, other objects and novel features of the invention will become apparent from the following specification and accompanying drawings which are merely exemplary.

In the drawings:

FIG. 1 is an enlarged sectional elevational view taken substantially along line 1-1 of FIG. 2 and showing a pressure gage to which the principles of the invention have been applied;

FIG. 2 is a front elevational view, on a reduced scale, of the gage shown in FIG. 1;

FIG. 3 is an enlarged sectional view of a detail of the back cover plate;

FIG. 4 is an edge view of the back cover plate;

FIG. 5 is a View of the back plate as seen when looking in the direction of the arrows in FIG. 4 on a reduced scale;

FIG. 6 is a section of a detail of the back cover plate; and

FIG. 7 is similar to FIG. 6 but shows a modification of the invention.

Referring to the drawings and particularly to FIGS. 1 and 2, the principles of the invention are shown as applied to a Bourdon type of pressure gage including a casing 10 of generally hollow cylindrical form and having both ends 11 and 12 open. A partition 13 divides the casing into two compartments 14 and 15. The usual pressure gage mechanism is housed within the compartment 15, and it is shown as including a Bourdon tube 16, the interior of which is connected to a threaded fitting 17 adapted to be connected to a line 18 containing fluid, the pressure of which is to be measured. The casing 10 may be made of any material, but is shown as being an injection molded plastic casing. The end of the Bourdon tube 16 opposite that including the fitting 17 is closed at 19, said closure being connected to a rigid element 20, one end of which is pivotally connected to an arm 21. The opposite end of arm 21 is pivoted to another link 22 which, in turn, is connected to a quadrant 23. The quadrant 2-3 is provided with a toothed sector 24 that meshes with a pinion 24 fixed to a spindle 26 on which an indicating hand 27 is fixed, as is well known.

A dial 28 is fixed to the partition 13 within chamber 14,

and a bezel 29 holds a transparent closure 30 in a manner to close the opening 11 in the casing 10.

The casing 10 may be provided with bosses 31 having passages therethrough for receiving bolts 32that thread into bosses or spacers 33 fixed to a mounting guard board 34; on which the gage is mounted in spaced relation for a purpose to be described later.

Adjacent the opening 12 may be provided a peripherally extending lip 35 (FIG. 3) and a groove 36 of greater diameter than the diameter of the lip 35. The lip 35 and the groove 36 extend completely around the inner peripheral surface of the opening 12.

. 4 without departing from the principles of the invention.

What is claimed is:

1. In a pressure gage, a hollow casing; gage mechanism ,within said casing; a front face closing one end of said casing; a cylindricalwall extending from said front face defining an opening in the back end of saidcasing; an internal peripheral lip and a peripheral groove of greater diameter than said lip on the back end of said cylindrical wall; a plastic back plate closing the back end of said does possess the desired characteristics and is ideally suited for the purposes intended.

The plate 37 may be generally circular'in form and may include a groove 38 producing a cross section at the bottom of the groove of substantially less thickness than the thickness of the remainder of the plate. With such a groove- 38, the plate is divided into two segments 39 and 40 which canbe flexed without danger of deteriorat ingthe material at the bottom" of groove 38.' In fact, continued flexing of the segments 39 and 40 actually increases the strength ofthe joint at'groove' 38, thereby providing a hinge pointof the plastic material forming the plate 37. a a

The peripheral edge 41 of the segment 40 may include spaced lips 42 and 43 (FIG 3) between which is located a groove 44 of less diameter than that of lips 42, 43, which lips 42,43 straddle the lip 35 on the casing 10 to hold the segment 40 in.closedposition.' The peripheral edge 45 of the segment 39 is flanged at 46, said flange being'adapted to be received within-the groove 36'within the casing 10. A depending extension 47 offlange 46 casing 10, and screws are adapted to pass through holes 49' therein which mate with similar threaded holes within casing 10. I 1

Referring to FIGS. 1, 5 and 6, the segment 40- 'may include an area 49 of generally circular extent; having a reduced cross section toward the center of the area. This construction provides a diaphragm effect toithe segment 40 so that upon the buildup of pressure within the casing 10, the circular area 49 will bulge outwardly (FIG. 6 thereby withdrawing the peripheral edge 41 of segment 40 inwardly and thereby releasing the intermeshing relation} ship between the lips 35, 42 and 43 so that the segment 40 can pivot about hinge joint or groove 38, thus releasing 'the pressure within'the casing 10. a a

A slot 50 may be provided in the segment 40 within which a screwdriver "blade or the like may be inserted to open the segment 40 when it is desired to adjust the gage mechanism'within chamber 15. Manually pressing inwardly on the area 49 will effect closing and latching of the segment 40 in closed position.- I

As shown in FIGS.4, 5 and 6, the hinge jointpro vided by the groove 38 is below the center of theback plate. In some gages, this may make adjustment of the gage mechanism difiicult. Referringito FIG. 7, it is within the scope of the present invention'to'reversethe plate so that the depending flange 47 is at the topof the back plate if such location more readily facilitates adjustment casing, said back plate having a reduced c'rosssection along a line dividing-said plate into two segments and forming a hinge joint between said segments; spaced I peripheral lips on one segment of said back plate adapted to cooperate with said internal'lip; and flange means on said'other segment adapted to cooperate with said groove for stationarily fixing said other segment to said casing.

2. Ina pressure gage, a casing; gage mechanism within said casing; a front face closing one end of said casing; cylindrical wall extending from said front face defining an opening in the back end of said casing; a plastic back plate'closing the back of said 'casing,peripheral means on said plate intereng aging with said wall at said backend, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; means for fixing one of said segments-stationarily to said casing; and an area of the non-stationary segment of less cross section than that of the remainder of said segment.

3. In a pressure gage, a hollow casing;-gage mechanism within said casing; a front face closing one end of said casing; a cylindrical wall extending from said front a 7 face defining an opening in the, back end of said casing; is adapted to be received-within a slot 48 (FIG. 1) of V I an internalperipheral lip and a peripheral. groove of greaterdiameter than said lip on the back end of said cylindrical wall; a plastic back plate closing the back end of said casing, said back plate having a reduced cross section along a linev dividing said plate into two segments and forming a hinge joint between said segments; spaced i peripheral lips on one segmentof'said back plate adapted to cooperate withsaid internallip; flange means on said other-segment adapted to cooperate with said groove for stationarily fixing said'other segment to said casing; 'and' 1 an area of the non-stationary segment of less cross section thanthat'of the remainder of said segment.

4. In apressure gage, "a hollow casing; gage mechanism within said casing; a front face closing one end of said casing; a cylindrical wallextending from said front face defining an opening in theback end of said casing;

of the gage mechanism. Furthermore, in the form shown a at internal peripheral lip and aperipheral groove of greater diameter than said lip on the back end of said cylindrical wall; a polypropylene back plate closing the back end of said casing, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; spaced peripheral lips on one segment of said back plate adapted to cooperate with said internal lip; and flange means on said other segment adapted to cooperate with said groove for stationarily fixing said other, segment to said casing. i i I T 5. In a pressure gage, a casing; gage mechanism within 1 said casing; a front face closing one end of said casing;

a polypropylene back plate closing the back of said casing, said back plate having a reduced cross section along a line dividing said plate into two segments and from the gage will intercept any parts ofthe gage mechanism Within the casing 10 that may fly out and possibly 7 1 it will beievident that changes may be made in such 'details and certain features-may be used withoutothers forming a hinge joint between said segments; means for -fixing one of said segments .stationarily to said casing;

and an area of the non-stationary segment ofless cross section than that of the remainder of said segment.

6. In a pressure gage, a hollowcasing; gage mecha nism within said casing; a front face closing one end of said casing; a cylindrical wall extending fromsaid front, facedefining an opening in the back end of said casing; an internal peripheral lip and a peripheral groove of greater diameter than said lip on the back end of said cylindrical wall;,a polypropylene back plate closing the back end of said casing, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; spaced peripheral lips on one segment of said back plate adapted to cooperate with internal lip; flange means on said other segment adapted to cooperate with said groove for stationarily fixing said other segment to said casing; and an area of the non-stationary segment of less cross section than that of the remainder of said segment.

7. Apparatus comprising in combination, a board; bosses mounted on said board; a pressure gage including a. casing having bosses adapted to be mounted on the bosses on said board to space said casing a substantial distance from said board; gage mechanism Within said casing; a front face closing one end of said casing; a cylindrical Wall extending from said front face defining an opening in the back end of said casing; an internal peripheral lip and a peripheral groove of greater diameter than said lip on the back end of said cylindrical wall; a plastic back plate closing the back end of said casing, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; spaced peripheral lips on one segment of said back plate adapted to cooperate with said internal lip; and flange means on said other segment adapted to cooperate with said groove for stationarily fixing said other segment to said casing.

8. Apparatus comprising in combination, a guard board; bosses mounted on said board; a pressure gage including a casing having bosses adapted to be mounted on the bosses on said board to space said casing a substantial distance from said board; gage mechanism within said casing; a front face closing one end of said casing; a cylindrical wall extending from said front face defining an opening in the back end of said casing; a plastic back plate closing the back of said casing, peripheral means on said plate interengaging with said wall at said back end, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; means for fixing one of said segments stationarily to said casing and an area of the non-stationary segment of less cross section than that of the remainder of said segment, said guard board serving to contain portions of said gage mechanism upon pivotal movement of said back plate during pressure blow out.

9. Apparatus comprising in combination, a board; bosses mounted on said board; a pressure gage including a casing having bosses adapted to be mounted on the bosses on said board to space said casing a substantial distance from said board; gage mechanism within said casing; a front face closing one end of said casing; a cylindrical wall extending from said front face defining an opening in the back end of said casing; an internal peripheral lip and a peripheral groove of greater diameter than said lip on the back end of said cylindrical wall; a polypropylene back plate closing the back end of said casing, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; spaced peripheral lips on one segment of said back plate adapted to cooperate with said internal lip; flange means on said other segment adapted to cooperate with said groove for stationarily fixing said other segment to said casing; and an area of the non-stationary segment of less cross section than that of the remainder of said segment.

10. In a pressure gage, a hollow casing; gage mechanism within said casing; a front face closing one end of said casing; a cylindrical wall extending from said front face defining an opening in the back end of said casing; an internal peripheral lip and a peripheral groove of greater diameter than said lip on the back end of said cylindrical wall; a back plate made from a plastic, the crystalline nature of which increases in strength through orientation and stretching, closing the back end of said casing, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; spaced peripheral lips on one segment of said back plate adapted to cooperate with said internal lip; and flange means on said other segment adapted to cooperate with said groove for stationarily fixing said other segment to said casing.

11. In a pressure gage, a casing; gage mechanism within said casing; a front face closing one end of said casing; a cylindrical wall extending from said front face defining an opening in the back end of said casing; a back plate made from a plastic, the crystalline nature of which increases in strength through orientation and stretching, closing the back of said casing, peripheral means on said plate interengaging with said wall at said back end, said back plate having a reduced cross section along a line dividing said plate into two segments and forming a hinge joint between said segments; means for fixing one of said segments stationarily to said casing; and an area of the non-stationary segment of less cross section than that of the remainder of said segment.

References Cited by the Examiner UNITED STATES PATENTS 448,449 3/91 Marsh 73--411 1,488,034 3/24 Crocker et al. 73-416 2,952,039 9/60 Jaffe.

RICHARD C. QUEISSER, Primary Examiner. DAVID SCHONBERG, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Net 3,201,992 August 24, 1965 Harry w. Hoff, Jr.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 58, for "24" read 25 column 3, line 23, for "point" read joint column 4, line 62, before "a" insert cylindrical wall extending from said front face defining an opening in the back end of said casing; line 63, before "said' insert peripheral means on said plate interengaging with said wall at said back end, column 5, line 5, after "with" insert said Signed and sealed this 5th day of April 1966.

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test:

NEST W. SWIDER EDWARD J. BRENNER esting Officer Commissioner of Patents 

1. IN A PRESSURE GAGE, A HOLLOW CASING; GAGE MECHANISM WITHIN SAID CASING; A FRONT FACE CLOSING ONE END OF SAID CASING; A CYLINDRICAL WALL EXTENDING FROM SAID FRONT FACE DEFINING AND OPENING IN THE BACK END OF SAID CASING; AN INTERNAL PERIPHERAL LIP AND A PERIPHERAL GROOVE OF GREATER DIAMETER THAN SAID LIP ON THE BACK END OF SAID CYLINDRICAL WALL; A PLASTIC BACK PLATE CLOSING BACK END OF SAID CASING, SAID BACK PLATE HAVING A REDUCED CROSS SECTION ALONG A LINE DIVIDING SAID PLATE INTO TWO SEGMENTS AND FORMING A HINGE JOINT BETWEEN SAID SEGMENTS; SPACED PERIPHERAL LIPS ON ONE SEGMENT OF SAID BACK PLATE ADAPTED TO COOPERATE WITH SAID INTERNAL LIP; AND FLANGE MEANS ON SAID OTHER SEGMENT ADAPTED TO COOPERATE WITH SAID GROOVE FOR STATIONARILY FIXING SAID OTHER SEGMENT TO SAID CASING. 